CA historical

The good news: Parts of California are finally getting some much needed precipitation. As Climate Central notes, “a series of Pacific storm systems is producing sorely needed rain and mountain snowfall in California, which has been suffering from one of its worst droughts in at least 500 years.”

The storms are being driven by an “atmospheric river,” which, as NOAA explains, is a “relatively narrow” region in the atmosphere “responsible for most of the horizontal transport of water vapor outside of the tropics.” Climate Central has the graphic:

atmospheric river

Satellite image of water vapor showing an atmospheric river approaching California from the tropics (square box). Credit: NOAA.

The bad news: Accuweather reports Friday that “In terms of the ongoing drought that has gripped parts of the West for years, the moisture with this system will only make a dent in the huge precipitation deficit that has occurred.”

As the map below reveals, for most of coastal and northern California, 15 to 36 (!) inches of rain would be needed to end the drought. But the northern half of California is projected to see only 2 to 4 inches of rain over the next several days, though some areas will see as much as 4-8.

curr-end-1mon

The ugly news: As the top chart from Bloomberg BusinessWeek reveals, California’s recent dry spells are growing longer and stronger.

This is consistent with my interviews of leading climate scientists and drought experts last week. Climatologist James Hansen told me, “Increasingly intense droughts in California, all of the Southwest, and even into the Midwest have everything to do with human-made climate change.” The warming by itself helps dry out the soil and reduce the snowpack, robbing the region of a reservoir needed for the summer dry season. But there is growing evidence that climate change and Arctic ice loss are leading to changes in weather patterns and stuck jet stream patterns of the exact kind that have been steering precipitation away from California over the past 12 months.

If the trend in warming-worsened droughts continues — and that seems inevitable given the world’s continued failure to reduce carbon pollution — then drought researcher Aiguo Dai’s warning will seem increasingly prescient: “The U.S. may never again return to the relatively wet conditions experienced from 1977 to 1999.” It is time to start planning for a permanent change in the climate of the West and Southwest.

The post California’s Recent Droughts Have Grown Longer And Stronger appeared first on ThinkProgress.